Control rod drive mechanisms for nuclear reactors typically require O-ring means for sealing the top closure, and these O-rings typically require the application of a predetermined amount of compressive force to seal properly. The conventional approach for applying this predetermined compressive force is by means of six jacking bolts evenly spaced on a bolt circle so as to apply an evenly distributed compressive force to the O-ring. When jacking bolts are used, it is necessary to torque the jacking bolts to a predetermined total torque in predetermined torque increments resulting in a multiplicity of torquing operations. Such torquing operations are very time consuming and the related apparatus, viz., jacking bolts and the abutment device for retaining same, is expensive. In addition, the cleaning and lubrication of the jacking bolts, which is required each time the closure assembly is removed, is a very time consuming operation.
Because of this it has been desirable to develop a device that evenly compresses the subject O-ring with a predetermined compressive force and permits retention of the O-ring in a compressed state after the device has been removed from the control rod drive mechanism.